There are significant advantages to combining a constellation of Low Earth Orbit (LEO) satellites and a constellation of Geosynchronous (GEO) satellites to provide a global communication system. Many prior art systems have been proposed using a single constellation and some have been proposed which use two or more constellations.
In satellite communication systems there are generally two classes of signaling data which are used to support and control the subscriber services offered by the system. In-band signaling is carried in the control channel and is closely associated with the service channel. In general, associated control channels share the same physical resources as the service channels, so they are usually very low data rate channels to avoid over-taxing the service channel resources and impairing the ability of the system to generate revenue. Out-of-band signaling is sent using other physical resources than those being used by the service channels. These signaling channels may or may not be carrying signaling data that is associated with an active service session.
Prior art hybrid systems have limitations because these prior art systems have not taken full advantage of the strength and weaknesses of each constellation type. The GEO satellites in the systems are limited because of their fixed position. GEO satellites provide better equatorial coverage but have more delay associated with them. Individual LEO satellites have limited coverage because of their relatively low altitude. LEO constellations provide better non-equatorial coverage and less delay.
What are needed are a method and apparatus which overcome these limitations and allow more efficient and less costly satellite communication systems to be constructed.